Integrated water testing system and method for ultra-low total chlorine detection

ABSTRACT

A dialysis system for determining an amount of total chlorine in a partially purified water sample is disclosed. The system includes a water machine that produces at least partially purified water including an at least partially purified water sample and a dialysis machine that provides a dialysis treatment to a patient. The dialysis machine receives the at least partially purified water from the water machine to prepare dialysis fluid for the dialysis treatment. The system also includes a total chlorine detector configured to receive the at least partially purified water sample, at a first time apply a source voltage to the at least partially purified water sample, and at a second time stop applying the source voltage to the at least partially purified water sample and instead monitor a sensed electrical parameter to determine an amount of total chlorine in the at least partially purified water sample.

PRIORITY CLAIM

This application is a divisional of U.S. patent application Ser. No.14/865,583, filed Sep. 25, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/797,086, filed on Mar. 12, 2013, now U.S. Pat.No. 9,162,021, which claims priority to U.S. provisional patentapplication Ser. No. 61/716,970, filed on Oct. 22, 2012, the entirecontents of each of which are incorporated herein by reference andrelied upon.

BACKGROUND

This application relates generally to water purity qualitative analysis,and in particular to water used for medical applications.

Water purity qualitative analysis determines the presence or absence andthe amounts of chemicals and their mixtures in water. Water purityqualitative analysis can require field kits for testing the waterfacilities. The field test kits are known in general to havedisadvantages including inaccuracies in data, false positives,limitations of single-factor testing, e.g., in measuring chlorine levelsin pools and spas, and overall accuracy. Disadvantages of fieldqualitative testing kits also include an inability to reproducestatistics. Outdoor and indoor conditions, such as humidity,temperature, wind, rain and noise add to the inherent disadvantages oftest kit qualitative field-type water monitoring.

Testing can alternatively be done by mixing water with powders in vials.Both strips and vials change the color of water to indicate if the waterpurity meets safe levels. Color change analysis leaves open thepossibility that the person viewing the change cannot see color well andthat multiple viewers may compare the water color to the test markersdifferently. Color viewing test results accordingly provide low tomoderate accuracy in measuring amounts of chlorine, bacteria and acidity(pH levels), which each affect water purity.

Sensors are used in municipal, industrial and residential water systemsto test variables affecting water purity for human consumption and use,as well as to monitor water purity for healthy ecosystems of otherliving organisms. Sensors measure temperature, pH levels anddesalination (salt control) compounds. However, using sensors inqualitative water purity field testing can result in drawbacks due tomoderate measurement accuracy for multiple types of water puritystatistics.

Using chemistry-based field-testing to gather qualitative water-puritydata gives incomplete statistical outcomes, similar to the pHcolorimetric qualitative testing. Operating at a neutral pH,chemistry-based testing, like colorimetric testing, measures particularaspects of inorganic substances in water, rather than all itscharacteristics. As an example, at neutral pH, both of thechemistry-based and colorimetric tests measure dissolved iron amounts,but not iron particles. In addition, ammonia levels from biologicaldecay compromise qualitative measurements using chemistry-based fieldtesting of nutrients in wastewater.

As discussed above, known water testing techniques have multipledrawbacks. In a medical setting in which the testing techniques arerelied upon, for example before allowing a therapy to take place, theramifications associated with inaccurate testing can be serious. If thewater testing underreports the level of a certain substance in thetested water, the water can be allowed to be used when it should not be,resulting in a potentially unsafe condition for the patient or in themalfunctioning of a machine running a medical treatment for the patient.The reverse situation is also problematic. If the testing isoversensitive, or in any case gives false positive or overreportedresults, the system may needlessly alarm or erroneously prevent atreatment from occurring.

Another problem with the above testing is its manual nature. Even if thetesting assay is otherwise sound, the patient or caregiver can introduceerror. And even if the testing and the operator performance are sound,manual testing still requires extra steps, adding time, complexity andcost.

An improved water quality system and method are needed accordingly.

SUMMARY

The present disclosure relates to water testing and in particular to thetesting of total chlorine (e.g., free chlorine and other similar boundactive chlorine species commonly known as chloramines) in water. Oneapplication for the testing apparatus and methodology of the presentdisclosure is to make water for use with online hemodialysis. Onlinehemodialysis makes dialysate from purified water. The purified water canbe made from house tap water. In a hospital or clinic, the house tapwater is the water found for example at sinks and drinking fountains inthe hospital or clinic. At home, the tap water is the patient's home tapwater.

Making dialysate from purified tap water involves adding salts to thepurified water. The goal is to achieve the electrolyte status of bloodplasma, or the water component of blood. Because hemodialysis works onthe principles of osmosis, diffusion and equilibration, the treatmentneeds to use a treatment fluid, or dialysate, that has the chemicalcomposition of purified blood. There are many components to thepatient's blood that are healthy and needed and should not be removedduring treatment. Red and white blood cells and platelets are examples.But these healthy and needed components are retained mechanically bymaking the pores in the dialyzer membranes too small for the cells andthe platelets to pass through from the patient or blood side of thedialyzer to the treatment or dialysate side of the dialyzer.

Salts or electrolytes such as a potassium, calcium, sodium and magnesiumare also, at least to a certain extent, healthy and needed components ofblood. But salts are dissolved in the blood water or plasma. Thus ifpure water were to be run as treatment fluid instead of dialysate, thelarge osmotic or diffusive gradient would pull too much of the salt fromthe blood and create a highly unsafe condition for the patient. For thatreason, great care is taken in the online manufacture of dialysate frompurified water to ensure that a desired amount of salt is present in thedialysate before the dialysate is allowed to be delivered to thedialyzer and osmotically or diffusively comingle with the patient'sblood.

One method for ensuring that a desired amount of salt is present in thedialysate is through the use of conductivity sensors. Adding salt to thepurified water generally increases electrical conductivity sensed by thesensors. The desired amount of salt will have a specific conductivity.The online machine mixes pure water and salts from concentratecontainers until the desired conductivity is sensed, after which thedialysate can be delivered to the dialyzer.

The online hemodialysis system contemplated for use with the presentapparatus and methodology employs a water purification system thatremoves preexisting salts, such as chlorine, from the incoming tap waterso that the dialysate generation portion of the system can begin withsalt-less, zero-conductivity water to which desired, blood-friendlysalts are added. Also, free chlorine in dialysate can cross the dialysismembrane and destroy the patient's red blood cells. Free chlorine insolution can also generate chloramines, which are known to inducehemolytic anemia. The useful lifetime of dialysis membranes is alsoshortened when free chlorine is present in dialysate. For at least thesereasons, AAMI/ANSI recommends that dialysate contain less than 0.5 mg/Lof free chlorine.

The present system and apparatus provide a way to automatically andprecisely detect either (i) the incoming total chlorine level of the tapwater or (ii) the total chlorine level present after the tap water hasflowed through a filter included to remove impurities such as activechlorine compounds (e.g., a filter check). The apparatus and method donot require input from the patient or caregiver. The apparatus andmethod are also accurate, so that the system alarms or otherwiseresponds when chlorine levels are too high but greatly reduces theamount of false trippings and needless treatment shutdowns.

In an embodiment, the system and corresponding method include a maintesting unit in fluid communication with an iodide reservoir and areducing agent reservoir. The iodide reservoir contains an iodide donoror a mixture of iodide donors, such as potassium iodide (“KI”) and/orsodium iodide (“NaI”). The reducing agent reservoir contains aspontaneous electron acceptor (e.g., a reducing agent) or a mixture ofspontaneous electron acceptors such as sodium sulfate (“Na₂SO₄”). Amembrane, such as a hydrophobic membrane, is provided with and dividesthe main unit into a reducing agent chamber and an iodide and samplechamber, which are in fluid communication with the reducing agentreservoir and the iodide reservoir, respectively. The main testing unitfurther includes an electrode pair capable of both generating tri-iodideand determining a resulting tri-iodide concentration. In oneimplementation, one electrode of the pair is in contact with fluid inthe reducing agent chamber and the other electrode of the pair is incontact with fluid in the iodide and sample chamber. In someembodiments, the iodide and sample chamber is a tube disposed within thereducing agent chamber, which can in turn be a larger diameter tube. Insome embodiments, the iodide and water sample chamber is in fluidcommunication with the reducing agent chamber via microchannels, forexample in a cassette.

In an embodiment, water quality is tested by determining a level oftotal chlorine. In such an embodiment, a water sample is provided to theiodide and sample chamber of the main testing unit, which is in fluidcommunication with the iodide reservoir, and is separated by themembrane from the reducing agent chamber, which is in turn in fluidcommunication with the reducing agent reservoir. Once the water sampleis pumped to the iodide and sample chamber, a baseline is measured. Thena voltage is applied to the electrode pair. The voltage producestri-iodide. This production of tri-iodide causes current to flow throughthe electrodes which, after a suitable relaxation period, is measuredvia the electrode pair.

In an embodiment, the concentration of total chlorine in water undertest is determined by measuring an initial, baseline current associatedwith any tri-iodide that may already be in the system (e.g., withoutgenerating any tri-iodide or adding external tri-iodide), followed byrepeated cycles of (a) generating tri-iodide by application of currentto the electrode pair and (b) measuring the resulting voltage in thesame electrode pair, typically after a suitable relaxation period. In anembodiment, the voltage is measured and converted to a currentmeasurement using Ohm's law. The plurality of voltage measurements (orcalculated current measurements) are plotted against relative orabsolute tri-iodide concentration. In this way, a calibration curveincluding a baseline, the test measurement, and several additional datapoints of known iodide concentration increases is created. The amount oftotal chlorine present in the water under test is proportional to thedifference in tri-iodide concentrations from subsequent cycles asdescribed above.

In some embodiments, the concentration of total chlorine in the waterunder test is determined from (a) a background voltage or currentmeasurement, (b) a baseline voltage or current measurement, and (c) fromone to about twenty cycles of (i) generating tri-iodide by applicationof current to the electrode pair and (ii) measuring the resultingvoltage in the same electrode pair after a suitable relaxation time. Thechoice of the number of cycles in step (c) will reflect a balancebetween accuracy of the total chlorine determination and the amount oftime required to perform the analysis. More cycles generally lead tomore accurate results. However, each cycle can take from several secondsto several minutes depending on operating parameters, and thus in theinterest of providing efficient and safe dialysis, the fewest number ofcycles in step (c) required to provide an accurate total chlorinedetermination is desired in one embodiment. Thus, in some embodiments,step (c) includes one to five cycles. In some embodiments, a firstdetermination of total chlorine includes a larger number of cycles instep (c), while subsequent determinations of total chlorine includefewer cycles in step (c). For example and without limitation, a firstdetermination of total chlorine in water under test includes three, fouror five cycles in step (c). A subsequent or a plurality of subsequenttotal chlorine determinations then includes one, two or three cycles instep (c).

It is accordingly an advantage that the water purification system andmethod of the present disclosure is performed automatically.

It is another advantage that the water purification testing system andmethod of the present disclosure is calibrated automatically.

It is a further advantage that the water purification testing system andmethod of the present disclosure is cleaned automatically.

It is yet another advantage that the water purification testing systemand method of the present disclosure is accurate.

It is yet a further advantage that the water purification testing systemand method of the present disclosure is low cost.

It is still another advantage that the water purification testing systemand method of the present disclosure is built into or packaged with awater purification system.

It is yet a further advantage that the water purification testing systemand method of the present disclosure requires minimal maintenance.

Still another advantage is that the disclosure is to provide a waterpurification testing apparatus and method that reduces user interaction.

Still a further advantage is that the water purification testing systemand method of the present disclosure outputs electrically for systemintegration.

Additional features and advantages are described herein, and will beapparent from, the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of one embodiment of a water purificationtesting system and method of the present disclosure.

FIG. 2 is a schematic view of one embodiment of an electrode pair of thepresent disclosure.

FIG. 3 is a schematic view of one representation of a mechanism in whicha sodium sulfate anion promotes the conversion of three iodide anions toone tri-iodide anion and two electrons in water.

FIG. 4 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

FIG. 5 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

FIG. 6 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

FIG. 7 is a schematic view of one embodiment of a water treatment systemwhich includes a detection cell of the present disclosure.

DETAILED DESCRIPTION

As discussed above, a more accurate and easier to use total chlorinesensor is needed to minimize the occurrences of false positives or tripsinherent with other chlorine testing methods (e.g., testing strips).False positive results are problematic in the purification of water forhemodialysis because they force users to stop treatment and performmaintenance. False negatives may result in an unsafe treatment beingperformed. The testing system and method discussed herein greatlyreduces the false tripping, can detect at least as low as 0.05 parts permillion (“ppm”) total chlorine concentration in one implementation,provides an automatic detection function (including calibration),built-in packaging, and the ability to be implemented with a relativelysmall incremental cost. In other embodiments, the testing system andmethod is capable of detecting 0.01 ppm total chlorine.

As used herein, the term, “total chlorine” refers to any and allreactive chlorine compounds including, but not limited to, chlorine gas(e.g., dissolved chlorine gas), hypochlorite, chloramines, andchloramine-T. Total chlorine may but does not have to exclude chlorideions (e.g., metal chlorides such as sodium chloride, potassium chloride,etc.).

In one embodiment, the water purity testing apparatus and associatedmethodology are integrated into a water purification machine, such asone set forth in U.S. Patent Publication No. 2011/0197971, entitled,“Water Purification System And Method”, filed Apr. 25, 2011, which is inturn used with an online hemodialysis machine, such as one set forth inU.S. Patent Publication No. 2009/0101549, entitled, “Modular AssemblyFor A Hemodialysis System”, filed Aug. 27, 2008, the entire contents ofeach of which are incorporated herein by reference and relied upon. Theelectrical and/or computer control units discussed below may be locatedin the water purification machine and/or the dialysis machine. The pumpsand valves discussed below are located in one embodiment within thewater purification machine. Thus, there can be electrical cablingrunning from the dialysis machine to the water purification machine tocontrol the pumps and valves located within the water purificationmachine. Alternatively, the water purification machine can also houseits own electrical and/or computer control unit for controlling thepurification units pumps and valves. Even here, however, the waterpurification control unit can communicate wired or wirelessly with thedialysis machine and be subordinate, for example, to the dialysismachine's master controller, e.g., sending chlorine data to same. Eitherone or both of the control units of the dialysis unit or the waterpurification unit could then place the overall system into an alarmstate if needed.

In one embodiment, the system and method of the present disclosuremeasure chlorine indirectly by allowing the molecule to oxidize iodideto tri-iodide and measuring the corresponding voltage change. Totalchlorine may be introduced into the system through many forms including,but not limited to, chlorine standard free chlorine (e.g., Cl₂ dissolvedin water), hypochlorite (e.g., as bleach), or chloramine-T. In apreferred embodiment, chloramine-T is used as a stabilized form of totalchlorine and is added to an iodide-containing reagent solution.Chloramine-T degrades to hypochlorite and hypochlorite in turn reactswith iodide via the following relationship to form tri-iodide:

ClO⁻+3I⁻+2H⁺↔I₃ ⁻+H₂O+Cl⁻

Calibration of the electrode system is achieved by electrochemicallygenerating tri-iodide and measuring the system response (voltage).Tri-iodide may be generated in multiple sessions to improve theestimation of the dependence of voltage with changes in tri-iodideconcentration. The amount of tri-iodide generated is computed frommeasured current moving though the electrode placed into potassiumiodide chamber. The current, in turn, is determined by measuring thevoltage change across a resistor of known value. Tri-iodide generationcan be accomplished using metals including, but not limited to, platinumand stainless steel, and by using SO₄ ⁻² as an auxiliary electrolyte. Inthis scenario, the electrochemical equations governing the generation oftri-iodide are:

3I⁻→I₃ ⁻+2e ⁻

SO₄ ⁻²+2e ⁻+4H⁺→SO₂+2H₂O

In one preferred embodiment, sulfate ions are introduced through sodiumsulfate and iodide ions are introduced as potassium iodide. Sodiumsulfate concentrations and potassium iodide concentrations above 5 g/Lhave been seen to yield reproducible generations of tri-iodidemolecules. Also in a preferred embodiment, the generation voltage ismaintained by a voltage source set to deliver 700 mV. The correspondinggenerating voltage ranges from 0.5 to 3.5 V and depends on theconcentration of iodide and sulfate ions.

Referring now to the drawings and in particular to FIG. 1, in oneembodiment an, e.g. embedded, testing system 10 provides two reagentreservoirs including an iodide reservoir or cell 12 and a reducing agentreservoir or cell 14. Iodide reservoir or cell 12 includes an iodidesource. Any iodide source may be used, provided that the iodide sourcecompletely dissociates in water. Non-limiting examples of iodide sourcesinclude alkaline iodide reagents such as potassium iodide (KI) and/orsodium iodide (NaI). Reducing agent reservoir or cell 14 includes areducing agent. Any suitable reducing agent may be used, provided thatthe reducing agent readily accepts electrons. One non-limiting exampleof a reducing agent is an alkaline sulfate such as sodium sulfate(Na₂SO₄). In one embodiment, iodide reservoir or cell 12 includespotassium iodide and reducing agent reservoir or cell 14 includes sodiumsulfate. System 10 also includes a main testing unit 20 that operateswith two electrical control circuits 30 and 40. Main testing unit 20includes a liquid-tight housing 22, which is separated into twocompartments 24 and 26 by a semi-permeable membrane 28 to allow chargedions to pass through the membrane, preventing an open circuit. Housing22 can be metal or plastic as desired. Compartments 24 and 26 can beopened or closed and sized to be the same or to have different volumesas desired. Membrane 28 can be a semipermeable membrane with a molecularweight cut-off (“MWCO”) of less than 1,000 Daltons, in one preferredembodiment less than 500 Daltons, and in another preferred embodimentfrom about 100 Daltons to about 500 Daltons. In some embodiments,membrane 28 is made of a material including one or more of: a polyethersulfone, a cellulose, and/or a nylon. In one embodiment, membrane 28 isan Ultracel PL-1 from Millipore (MWCO 1000). In some embodiments, themembrane allows only positive charge to penetrate. In some embodiments,the membrane allows only negative charges to penetrate. In someembodiments, the membrane allows both positive and negative charges topenetrate.

Reagent reservoirs 12 and 14 are both in valved and pump communicationwith main testing unit 20. In an embodiment, the iodide reservoir 12and/or the reducing agent reservoir 14 are provided in a cartridge orcassette form. In an embodiment, the cartridge includes iodide reservoir12 and reducing agent reservoir 14. In another embodiment, the cartridgeor cassette includes iodide reservoir 12, reducing agent reservoir 14,and electrodes 42 a and 42 b for circuitry 40. In an embodiment, theiodide is provided in a liquid form such as a pre-mixed solution or aconcentrate, or in a solid form such as a crystal, a powder, and/or atablet. In some embodiments, the iodide reservoir includes potassiumiodide. In an embodiment, the reducing agent is provided in a liquidform such as a pre-mixed solution or a concentrate, or in a solid formsuch as a crystal, a powder, and/or a tablet. In some embodiments, thereducing agent reservoir includes sodium sulfate. When either reagent isprovided in dry form, the associated control unit can control theassociated pumps and valves to first pump water into the crystal, drypowder or tablet containers for mixing before pumping liquid iodidereagent or reducing agent from the containers.

In the embodiment illustrated in FIG. 1, the iodide cell or reservoir 12communicates fluidly with the iodide reagent and sample chamber orcompartment 24 of main testing unit 20 via line 52 a including a valve16 a and pump 18 a. Reducing agent cell or reservoir 14 in turncommunicates fluidly with chamber or compartment 26 of main testing unit20 via line 52 b including valve 16 b and pump 18 b.

FIG. 1 also illustrates that the main testing unit 20 is fluidlyconnected to a water purification unit or machine 50, which can be thewater purification machine described above in the incorporated U.S.2011/0197971 Publication. In the illustrated embodiment, there aremultiple fluid connections between water purification machine 50 andmain testing unit 20. In particular, test water is pumped from a testwater outlet or supply 58 of water purification machine 50 to iodide andsample chamber or compartment 24 of main testing unit 20 via line 52 c,including valve 16 c and pump 18 c. Deionized (“DI”) water is pumpedfrom DI water outlet or supply 56 of water purification machine 50 toiodide and sample compartment 24 of main testing unit via line 52 d,including valve 16 d and pump 18 d. Drainage water is pumped from theiodide and sample compartment 24 of main testing unit 20 to a drain 54of water purification machine 50 via line 52 e, including valve 16 e andpump 18 e.

Drainage water is also pumped from reducing agent chamber or compartment26 of main testing unit 20 to drain 54 of water purification machine 50via line 52 f, including valve 16 f and pump 18 f. DI water is alsopumped from DI water outlet or supply 56 of water purification machineto reducing agent compartment 26 of the main testing unit via line 52 g,including valve 16 g and pump 18 g.

In an alternative embodiment, a single drain pump (18 e or 18 f) is usedinstead of the separate drain pumps illustrated and drain valves 16 eand 16 f are sequenced to selectively drain from one or both of chambersor compartments 24 and 26. Alternatively or additionally, a single DIpump (18 d or 18 g) is used instead of the multiple DI pumps illustratedand DI valves 16 d and 16 g are sequenced to selectively pump DI waterto one or both of chambers or compartments 24 and 26. Thus, the numberof pumps shown in FIG. 1 can be reduced by at least two pumps from thenumber of pumps illustrated.

As described in further detail below, chlorine testing is performedusing the valves and pumps provided or operable with lines 52 a to 52 cin association with the circuit 40 and electrode pair 42 a and 42 b.Calibration is performed using the valves and pumps provided or operablewith lines 52 a, 52 b, 52 d and 52 g in association with circuit 40 andelectrodes 42 a and 42 b. Rinse is performed using the valves and pumpsprovided or operable with lines 52 d to 52 g.

Determination of the total chlorine content of the water test sample issensitive to the volume of the water test sample provided. Accordingly,in an embodiment, the amount of test sample water is accurately meteredand/or pumped into main test unit 20 by, for example, a microfluidicpump. One suitable microfluidic pump is a SmoothFlow™ pump provided byMicrofluidica, LLC (Glendale, Wis.). Although any amount of water undertest may be used, typically a small volume, for example from about 50 μLanywhere to about 500 μL of water under test are pumped into maintesting unit 20.

In an embodiment, pumps 18 a to 18 g are electrically operated pumps,such as microfluidic pumps, and can be gear, centrifugal, piston or vanepumps. The pumps may have liquid contacting surfaces that are made ofmedical grade plastic or stainless steel, such that the surfaces cannotthemselves corrode or contaminate water, such as test, DI or drainwater, running past the surfaces, or they may have liquid contactingsurfaces that may contaminate the fluid if placed in the drain line. Inan alternative embodiment, pumps 18 a to 18 g are small peristaltic(roller or linear) or tube actuating (e.g., shuttle) pumps that pumpwater, such as test, DI or drain water, through a respective tube bycollapsing, squeezing and/or crushing the tube sequentially to move thefluid. In another alternative embodiment, pumps 18 a to 18 g areelectrically and/or pneumatically actuated membrane pumps that movewater, such as test, DI or drain water, by fluctuating a membrane backand forth between a chamber of known volume. Pumps 18 a to 18 g canfurther alternatively be any combination of the above types of liquidpumps, selected to optimize performance, cost and reliability.

It should be appreciated from the above discussion of the various typesof pumps 18 a to 18 g, that lines 52 a to 52 g can be made of differentmaterials, such as stainless steel or plastic. Suitable plastics includepolyvinylchloride (“PVC”), for example, when lines 52 a to 52 g do nothave to be deformed for, e.g., peristaltic or shuttle pumping, orsilicone, for example, when lines 52 a to 52 g are deformed for, e.g.,peristaltic or shuttle pumping. If membrane pumps are used, lines 52 ato 52 g may contain sections that transition to a chamber havingmembrane sheeting, which can likewise be plastic, such as PVC sheeting.

Each of valves 16 a to 16 g can be an electrically or pneumaticallyactuated valve. In an embodiment, valves 16 a to 16 g include a valvehousing to which the respective line 52 a to 52 g is sealingly attached.Here, each line 52 a to 52 g can be broken and sealingly attached toinlet and outlet connectors of the respective valve 16 a to 16 g. Alsohere, the valve includes its own internal opening/shutting mechanism.Alternatively, valves 16 a to 16 g are electrically or pneumaticallyactuated solenoid valves that operate directly on lines or tube 52 a to52 g, e.g., compressible plastic tubes. The solenoid valves can forexample be fail-safe or spring-operated closed and electrically orpneumatically actuated open. In a further alternative embodiment, valves16 a to 16 g are electrically and/or pneumatically actuated membranevalves, for example, provided as part of a disposable cassette thatincludes a hard, valve chamber part that is sealed fluidly by one ormore flexible, e.g., PVC, sheet that is flexed to close and open thehard part of the chambers. Here, the hard part can also be formed withpump chambers and the same one or more flexible sheet can be used forpumps 18 a to 18 g. Valves 16 a to 16 g can further alternatively be anycombination of the above types of liquid valves, selected to optimizeperformance, cost and reliability.

System 10 includes a control unit 60, which in the illustratedembodiment is housed inside water purification machine 50. Control unit60 can include one or more processor, one or more memory and one or morecontrol circuitry, such as control circuit 40. Pumps 18 a to 18 g andvalves 16 a to 16 g can be operated under the control of a computerprogram stored at control unit 60. Control unit 60 is in one embodimentthe same control unit 60 used for all of water purification machine 50.Hence, control unit 60 may include a master processor that communicates(i) with a user interface 62 of water purification machine 50, (ii) witha wired or wireless data link to a corresponding control unit 110 ofdialysis machine 100 that uses water produced by water purificationmachine 50, and (iii) with one or more delegate processor that runs theelectrical equipment provided within water purification machine 50,including pumps 18 a to 18 g and valves 16 a to 16 g. Either one or bothof the master and delegate processors of control unit 60 may receivesignal inputs from and send signal outputs to control circuit 40.

In one embodiment, the master processor sends output data, such aschlorine content output data, to one or both of a user interface ofwater purification machine 50 and/or to the control unit 110 of thedialysis machine 100. It is contemplated for dialysis machine 100 to siton top of water purification machine 50. Thus, either user interface 62of water purification machine 50 and/or user interface 112 of dialysismachine 110 could be used to inform the patient or caregiver of thechlorine results and to communicate any associated alerts or alarms. Inone embodiment, however, main user interface 112 of dialysis machine 110is a wireless, e.g., tablet, user interface that allows the patient orcaregiver to reside remotely from the dialysis machine while stillviewing information concerning same. Here, it is desirable to send waterpurification machine 50 data, such as chlorine content data, via controlunit 60 to control unit 110 of dialysis machine 100, which in turnforwards the pertinent data to remote user interface or tablet 112.

In an alternative embodiment, the generation and receipt of signals toand from control circuit 40 and the control of pumps 18 a to 18 g,valves 16 a to 16 g and possibly other electrical components of waterpurification machine 50 is done via control unit 110 of the dialysismachine 100. Here again, control unit 110 of dialysis machine 100 canforward pertinent data to the remote user interface or tablet 112 ofdialysis machine 100. When control unit 110 of machine 100 is theprimary control unit for water purification system 10, control unit 60may be eliminated, at least as far as system 10 is concerned, or limitedto a smaller number of tasks.

In any case, control unit 60 and/or control unit 110 opens valves 16 ato 16 g and operates pumps 18 a to 18 g to meter into chambers orcompartments 24 and 26 precise amounts of desired fluids, e.g., DIwater, iodide solution, reducing agent solution or test water solution,or to remove precise amounts of fluids from chambers or compartments 24and 26 to drain 54. The metering can be run open loop and rely on theaccuracy of the pumping mechanism to deliver the correct ratio offluids. Alternatively or additionally, feedback in the form ofconductivity sensing may be used to ensure that the proper proportioningof fluids takes place within chambers or compartments 24 and 26.

As illustrated, in an embodiment, main unit 20 is placed in fluidcommunication with deionized water via outlet or storage 56 from waterpurification unit 50. Deionized water is pumped into the main unit(e.g., into the chambers or the compartments 24 and 26 separately) toflush the water test sample and any residual tri-iodide and/or totalchlorine from the main unit. In some embodiments, the total chlorinelevel is determined before and/or during each dialysis treatment. Here,an aliquot of water from water purification unit 50 for making dialysateis diverted to system 10 and analyzed by the methods disclosed hereinbefore any water from purification unit 50 is allowed to be used to makedialysate at machine 100. Control unit 60 or 110 can be programmed toprevent and/or suspend dialysis fluid preparation when the totalchlorine level in the dialysis water exceeds a threshold level, forexample 0.1 ppm. In some embodiments, water from purification unit 50 isanalyzed after a dialysis treatment is completed, such that correctiveaction can be taken to reduce total chlorine levels in the water beforea subsequent dialysis treatment is required, and providing typically atleast twenty-four hours before the subsequent treatment.

As discussed above, system 10 can be implemented within waterpurification unit 50. If so, main unit 20 can be positioned downstreamof one or more filter used in water purification unit as specified inthe U.S. 2011/0157971 Publication. For example and without limitation,main unit 20 may be in fluid communication with a carbon filter, whereinwater exiting the carbon filter, or samples thereof, is then tested fortotal chlorine compounds according to the present disclosure. A failedtest likely means that the carbon filter is faulty or spent and needsreplacement. A suitable message can then be displayed, e.g., on userinterface 112 of dialysis machine 100.

Electrical circuit 40 operates via electrodes 42 a and 42 b to performboth calibration and total chlorine sensing. Electrode 42 a is insertedinto iodide and sample compartment 24, while electrode 42 b is insertedinto reducing agent chamber or compartment 26. Electrodes 42 a and 42 bcan be metallic. In some embodiments, electrodes 42 a and 42 b are eachprovided with or are in electrical communication with a resistor (e.g.,a 1 kΩ to 5 kΩ resistor). As described above, the iodide solution andthe reducing agent solution are separated by membrane 28, which permitselectricity but not fluid to flow across the membrane. In oneembodiment, membrane 28 includes micropores or perforations in themembrane, which are formed such that there are about three (3) to abouttwenty (20) holes, each hole sized such that charge can freely passbetween the chambers without any fluid passing between the chambers. Inone example embodiment, the membrane is formed of a silicone elastomericmaterial and includes about seven micropores formed by a 28-gaugeneedle. The elastomeric nature of the membrane causes the holes tosubstantially close, allowing electrical charge to pass through withoutpermitting fluid to pass between the chambers. One suitable membrane 28is made of silicone tubing. Another suitable membrane 28 is provided byMillipore and is sold under the trade name ULTRACEL PL-1. When a voltageis applied to electrical circuit 40 (e.g., about 1 volt DC), the inducedcurrent generates tri-iodide from the iodide solution in an amountproportional, for example, to the amount of total chlorine present inthe water sample.

Electrical circuit 40 also detects the amount of tri-iodide generated atthe first electrical control circuit. Here, electrical control circuit40 is a tri-iodide detection circuit in which electrodes 42 a and 42 bcan be, e.g., platinum, stainless steel, gold, or combinations or alloysthereof. When a low voltage is applied across electrodes 42 a and 42 b,the induced current can be measured and used as a proxy for the amountof tri-iodide in the solution, and therefore the amount of totalchlorine in the water sample. In some embodiments, the system is capableof determining an amount of total chlorine in the water sample as low asabout 0.05 ppm.

In one embodiment shown in the sectioned view of FIG. 2, testing unit 20is provided, at least in part, as a tubing assembly 200. The iodide andsample chamber or compartment 24 is a tube 214 disposed within areducing agent chamber or compartment 26, which is also a tube 216, andwhich is of a larger diameter than that of tube 214 (chamber 24). Insome embodiments, the outer reducing agent tube 216 has an innerdiameter that is about 1.5 to about 4 times larger the outer diameter ofthe inner iodide and sample tube 214. Tube 214 (chamber 24) is in fluidcommunication with iodide reservoir 12 (not illustrated in FIG. 2),while tube 216 (chamber 26) is in fluid communication with reducingagent reservoir 14 (not illustrated in FIG. 2). The inner iodide andsample tube 214 includes or defines a plurality of perforations 214 a,(membrane 28) e.g., hydrophobic perforations, which do not allow fluidto pass between chambers 24 and 26, but permit electrical conductivityto flow between the chambers (through the wall of narrower tube 214 intothe outer diameter of larger tube 216).

The inner iodide and sample tube 214 is also in fluid communication withwater to be tested (not illustrated in FIG. 2), which is pumped via line52 c and pump 18 c from test sample outlet 58 of water purificationmachine 50. The tri-iodide generation loop of electrical circuit 40includes electrodes 42 a and 42 b, each having or being in electricalcommunication with a respective resistor 46 and 48 (e.g., a 1 kΩresistor). Electrode 42 a of electrical circuit 40 is placed in contactwith the fluid in the inner iodide and sample tube 214, while the otherelectrode 42 b is placed in contact with the fluid in the outer reducingagent tube 216. In the illustrated embodiment, electrode 42 b isgrounded. As mentioned above, electrodes 42 a and 42 b can be formed ofdurable metal such as platinum, stainless steel, gold, copper, or becombinations or alloys thereof.

A voltage source 44 is provided (e.g., as part of electronics 40 or aspart of control unit 60 or 110) to apply of a voltage, such as fromabout 0.7 VDC to about 1.0 VDC. The voltage source across the setresistance of resistors 46 and 48 generates a desired current. Theapplied current generates tri-iodide in the iodide and sample tube 214.

In one embodiment, control unit 60 or 110 causes the voltage to beapplied for a period of time from about one minute to about ten minutes,for example about one minute, about two minutes, about three minutes,about four minutes, about five minutes, about six minutes, about sevenminutes, about eight minutes, about nine minutes, or about ten minutes.

As discussed, in the illustrated embodiment, the electrical circuit 40is also configured to measure voltage across membrane 28 or 214 a. In anembodiment, when it is desired to measure the voltage across membrane 28or 214 a, control unit 60 or 110 causes the voltage from voltage source44 used to generate tri-iodide to cease. Thereafter, control unit 60 or110 causes the electrical circuit 40 to measure the voltage differencebetween the iodide and sample compartment 24 (tube 214) and the reducingagent chamber or compartment 26 (tube 216). In one embodiment, a voltagemeter 45 measures the voltage across resistor 46.

In some embodiments, control unit 60 or 110 causes the voltage to bemeasured about once per second and anywhere in duration from about oneminute to about 10 minutes, e.g., for example about 1 minute, about 2minutes, about 3 minutes, about 4 minutes, about 5 minutes, about 6minutes, about 7 minutes, about 8 minutes, about 9 minutes, or about 10minutes. The measured voltage is proportional to the concentration oftri-iodide, which is in turn proportional to the amount of totalchlorine in the water sample. In some embodiments, the measured voltageis a steady state voltage.

In one embodiment, iodide reservoir 12 is a chamber holding an iodidesolution of known concentration, and which is in fluid communicationwith the iodide and sample chamber 24 as shown and discussed above. Insome embodiments, iodide reservoir 12 holds about 0.1 gram to about onegram of iodide reagent (e.g., potassium iodide) in about one to about 10mL of water. In some embodiments, the iodide reagent is a solution ofabout 0.25 gram to about 0.7 gram of iodide reagent in three to seven mLof water. In some embodiments, iodide reservoir 12 contains at leastenough iodide reagent to last about one month or longer, e.g., from onemonth to six months, for example, so that refilling iodide reservoir 12does not reduce the normal maintenance cycle of water purification unit50. In some embodiments, the iodide reagent itself has a level of totalchlorine that is below the detection limit for the system. In someembodiments, the iodide reagent has less than 0.1 ppm, less than 0.05ppm, or less than 0.01 ppm of any total chlorine compound.

Reducing agent reservoir 14 is a chamber holding a reducing agent, suchas a solution comprising a reducing agent. In some embodiments, thereducing agent reservoir includes about two to about twenty grams of areducing agent (e.g., an alkaline sulfate such as sodium sulfate) in asuitable amount of water. In some embodiments, the reducing agentreservoir 14 holds about seventeen grams of reducing agent. In someembodiments, reducing agent reservoir 14 contains at least enoughreducing agent to last about one month or longer, e.g., from one monthto six months, for example, so that again refilling reducing agentreservoir 14 does not reduce the normal maintenance cycle of waterpurification unit 50.

In one preferred implementation, one mole of tri-iodide is generated foreach mole of total chlorine. In some embodiments, the pump speeds of oneor more or all of concentrate pumps 18 a and 18 b and test sample pump18 c are adjusted to optimize the ratio of moles of tri-iodide formedper moles of total chlorine in the water under test. In someembodiments, a higher pump speed generates closer to about one mole oftri-iodide per mole of total chlorine than a slower pump speed underotherwise identical conditions.

In some embodiments, chloramine-T is used as an artificial totalchlorine source to optimize or calibrate pump speed based upon themeasured current in the tri-iodide detection cell. In such anembodiment, a water sample with known total chlorine concentration maybe prepared by combining a water sample with no or essentially no totalchlorine content with a known amount of chloramine-T. The resultingwater sample having a known total chlorine concentration may then beused to test the sensor, calibrate the system, or optimize pump speed.

In an embodiment, control unit 60 or 110 automatically performs multipletotal chlorine determinations and averages the discrete results. It isalso contemplated for system 10 to use an agitator, such as anultrasonic vibrator, to agitate testing unit 20 during the test cycle topromote connectivity between the tri-iodide generation cell (chamber 24)and the tri-iodide detection cell (chambers 24 and 26). Other suitablemixing mechanisms include (but are not limited to): baffles, stirrers,agitators, vibration mechanisms, or any other suitable stirringmechanisms.

FIG. 3 illustrates the principle of the electrochemical reaction. Inaqueous solution, one equivalent of sulfate (SO₄ ⁻²) promotes theconversion of three iodide anions (I⁻) to one tri-iodide anion (I₃ ⁻).The process consumes four equivalents of protons while producing oneequivalent of SO₂ and one equivalent of water, and simultaneouslyliberating two electrons (e⁻). When iodide anions are present in excesscompared to the amount of total chlorine, the amount of tri-iodideproduced is directly proportional to the amount of total chlorinepresent.

Example Methodology

In some embodiments, control unit 60 or 110 causes a process fordetermining an amount of total chlorine in the water under test toinclude:

(a) providing a total chlorine detection system as disclosed herein;

(b) providing a water sample, the water sample including an amount oftotal chlorine;

(c) measuring a background voltage V_(B) in an electrode pair;

(d) metering an amount of the water sample into the system;

(e) monitoring a baseline voltage V₀ in the electrode pair, optionallyfor a time t₀, the baseline voltage V₀ associated with tri-iodide in thewater sample, wherein the amount of tri-iodide in the water sample isassociated with the amount of total chlorine in the water sample;

(f) generating a first amount of tri-iodide from the water sample byapplying a voltage V₁ to the electrode pair for a time t₁;

(g) thereafter monitoring a first voltage V₂ in the electrode pair,optionally for a time t₂, the first voltage V₂ associated with the sumof the amount of total chlorine and the first amount of tri-iodide;

(h) thereafter generating a second amount of tri-iodide from the watersample by applying a voltage V₃ to the electrode pair for a time t₃;

(i) thereafter monitoring a second voltage V₄ in the electrode pair,optionally for a time t₄, the second voltage V₄ associated with the sumof the amount of total chlorine and the first and second amounts ofgenerated tri-iodide;

(j) thereafter optionally generating a third amount of tri-iodide fromthe water sample by applying a voltage V₅ to the electrode pair for atime t₅;

(k) optionally monitoring a third voltage V₆ in the electrode pair for atime t₆, the third voltage V₆ associated with the sum of the amount oftotal chlorine and the first, second and third amounts of generatedtri-iodide; and

(l) calculating the amount of total chlorine in the water sample usingat least one of the baseline voltage V₀, the first voltage V₂, thesecond voltage V₄, and the optional third voltage V₆, wherein each ofthe baseline voltage V₀, the first voltage V₂, the second voltage V₄,and the optional third voltage V₆ are corrected by first subtracting thebackground voltage V_(B).

In some embodiments, the method also includes:

(m) repeating steps (g) to (k) to generate fourth, fifth, and sixthmonitored voltages V₈, V₁₀ and V₁₂, respectively, before step (l); and

(n) including the fourth, fifth, and sixth monitored voltages V₈, V₁₀and V₁₂, respectively, in the calculation of step (l) after correctingfor any background voltage V_(B).

In some embodiments, the method further includes:

(o) repeating steps (g) to (h) an additional time to generate a seventhmonitored voltage V₁₄ before step (l); and

(p) including the seventh monitored voltage V₁₄ in the calculation ofstep (l) after correcting for any background voltage V_(B).

The calculation step (l) can be accomplished using any suitable dataanalysis means based on one or more of the baseline voltage V₀ and firstmonitored voltage V₂, second monitored voltage V₄, optional thirdmonitored voltage V₆, optional fourth monitored voltage V₈, optionalfifth monitored voltage V₁₀, optional sixth monitored voltage V₁₂, andoptional seventh monitored voltage V₁₄. In an example methodology,calculating the total chlorine concentration in the water sample in step(l) above includes:

(i) plotting the plurality of monitored voltage values (e.g., V₂, V₄,V₆, V₈, V₁₀, V₁₂, etc.) (y-axis), optionally corrected for anybackground voltage V_(B), as a function of relative tri-iodideconcentration, wherein the first relative tri-iodide concentration isset to x=0; and

(ii) extrapolating a line of best fit using at least two of theplurality of monitored voltage values V₂, V₄, V₆, etc., optionallycorrected for any background voltage V_(B), to a point where y is equalto the baseline voltage V₀ and correlating that point to determine thex-value (“x₀”) associated with said point, wherein the unknown totalchlorine concentration is equal to (−1)(x₀).

In any embodiment described herein, the monitored voltages V₀, V₂, V₄,V₆, V₈, V₁₀, V₁₂, etc., can be corrected to exclude any backgroundtri-iodide present in the system by subtracting the background voltageV_(B) from each monitored voltage value. In other embodiments,background tri-iodide present in, for example, the iodide reagent, canbe reduced, minimized or eliminated by reversing the polarity of thetri-iodide generation electrode and applying a suitable voltage for aperiod of time sufficient to convert any background tri-iodide to iodidebefore introduction of a water sample.

In some embodiments, the applied voltages V₁, V₃, V₅, V₇, etc. are allthe same or substantially the same.

In some embodiments, control unit 60 or 110 causes tri-iodide generatingtimes t₁, t₃, t₅, t₇, t₉, . . . , to be substantially the same,essentially the same, or the same. In some embodiments, control unit 60or 110 causes tri-iodide generating times t₁, t₃, t₅, t₇, t₉, . . . , toeach be about one minute to about ten minutes, for example about oneminute, about two minutes, about three minutes, about four minutes,about five minutes, about six minutes, about seven minutes, about eightminutes, about nine minutes, or about ten minutes. In some embodiments,tri-iodide generating times t₁, t₃, t₅, t₇, t₉, . . . , are each aboutfive minutes.

In some embodiments, control unit 60 or 110 causes voltage monitoringtimes t₂, t₄, t₆, t₈, t₁₀, . . . , to be substantially the same,essentially the same, or the same. In some embodiments, control unit 60or 110 causes voltage monitoring times t₂, t₄, t₆, t₈, t₁₀, . . . , toeach be about one minute to about ten minutes, for example about oneminute, about two minutes, about three minutes, about four minutes,about five minutes, about six minutes, about seven minutes, about eightminutes, about nine minutes, or about ten minutes. In some embodiments,control unit 60 or 110 causes voltage monitoring times t₂, t₄, t₆, t₈,t₁₀, . . . , to each be about five minutes.

In some embodiments, control unit 60 or 110 causes the voltage to bemonitored by measuring the voltage a single time. In alternativeembodiments, control unit 60 or 110 causes the voltage to be monitoredby measuring a voltage at a rate of about one measurement per tenseconds (e.g., 0.1 Hz) to about ten measurements per second (e.g., 10Hz), for example about 0.1 Hz, about 0.2 Hz, about 0.3 Hz, about 0.4 Hz,about 0.5 Hz, about 0.6 Hz, about 0.7 Hz, about 0.8 Hz, about 0.9 Hz,about 1 Hz, about 2 Hz, about 3 Hz, about 4 Hz, about 5 Hz, about 6 Hz,about 7 Hz, about 8 Hz, about 9 Hz, or about 10 Hz. In some embodiments,the voltage is measured a plurality of times during the measurement timeperiod, for example about five times, about six times, about seventimes, about eight times, about nine times, about ten times, aboutfifteen times, about twenty times, about thirty times, about fortytimes, about fifty times, about sixty times, about seventy times, abouteighty times, about ninety times, about 100 times, about 150 times,about 200 times, about 250 times, about 300 times, about 350 times,about 360 times, about 400 times, about 450 times, about 500 times,about 550 times, about 600 times, about 650 times, about 700 times,about 750 times, about 800 times, about 850 times, about 900 times,about 950 times, about 1000 times, about 1200 times, about 1500 times,about 1800 times, about 2000 times, about 2400 times, about 2500 times,about 3000 times, about 3500 times, about 3600 times, about 4000 times,about 4200 times, about 4500 times, about 4800 times, about 5000 times,about 5400 times, about 5500 times, or about 6000 times during thevoltage measurement time period.

In some embodiments, control unit 60 or 110 causes the voltage to bemeasured one time per second over the course of one minute.

In some embodiments, control unit 60 or 110 causes an amount of timebetween a voltage monitoring step (e.g., any one of steps (f), (h), (j),etc.) and a subsequent tri-iodide generation step (e.g., any one ofsteps (g), (i), (k), etc.) to be sufficient to allow the tri-iodideand/or the voltage to equilibrate. In some embodiments, control unit 60or 110 causes the amount of time is about one minute to about tenminutes, for example about one minute, about two minutes, about threeminutes, about four minutes, about five minutes, about six minutes,about seven minutes, about eight minutes, about nine minutes, or aboutten minutes. In some embodiments, an amount of time between steps (d)and (e) is no less than about one minute, about two minutes, about threeminutes, about four minutes, about five minutes, about six minutes,about seven minutes, about eight minutes, about nine minutes, or aboutten minutes.

In some embodiments, control unit 60 or 110 causes the amount of timebetween a tri-iodide generating step (e.g., any one of steps (e), (g),(i), etc.) and a subsequent voltage monitoring step (e.g., any one ofsteps (f), (h), (j), etc.) is sufficient to allow the tri-iodide and/orthe voltage to equilibrate. In some embodiments, the amount of time isabout ten seconds to about five minutes, for example about ten seconds,about fifteen seconds, about twenty seconds, about thirty seconds, aboutforty seconds, about forty-five seconds, about fifty seconds, about oneminute, about 1.25 minutes, about 1.5 minutes, about 1.75 minutes, abouttwo minutes, about 2.25 minutes, about 2.5 minutes, about 2.75 minutes,about three minutes, about 3.25 minutes, about 3.5 minutes, about 3.75minutes, about four minutes, about 4.25 minutes, about 4.5 minutes,about 4.75 minutes, or about five minutes.

Example Method of Calculation

Control unit 60 or 110 can be programmed to perform the followingcalculations.

Calculation 1. Average the last thirty readings of each period followinga chlorine addition or electrochemical generation of iodide.

Calculation 2. Compute the average change in voltage with tri-iodideconcentration by plotting the change in measured voltage (y-axis)between successive periods of tri-iodide generation (x-axis). Usemeasured current to compute the amount of tri-iodide ([I₃ ⁻]) generatedas:

[I ₃ ⁻]=i*t/2F*V,

where i=current (A or charge/s), t=time (s), F=Faraday's constant(charge/mole of electrons), V=iodide reagent solution volume (L), and 2represents the number of electrons transferred between iodide andtri-iodide.

Calculation 3. Divide difference of the voltage measured before theaddition of total chlorine and the voltage measured after the additionof chlorine by the computed slope to calculate the tri-iodideconcentration of the water sample.

Example Operation

Step 1. Add 0.25 gram to 0.7 gram of KI and 3 mL to 7 mL of water to theKI reservoir, and two grams to twenty grams of Na₂SO₄ and 225 mL waterto the Na₂SO₄ reservoir.

Step 2. 200 μL of water under test are then pumped via, e.g., amicrofluidic pump, into the KI and water sample chamber 24 of the mainunit.

Step 3. 700 mV is then applied to electrode pair 42 a and 42 b togenerate tri-iodide. Optionally, the main unit is agitated to promotemass transfer.

Step 4. The voltage across electrode pair 42 a and 42 b is thenmeasured.

Step 5. Steps 2 to 4 are repeated twice to ten times.

Step 6. Lines 52 d, 52 e and 52 f are then opened and the main unit isflushed with DI water.

Step 7. The voltage values recorded in each iteration of Step 4 are usedin comparison to calibration data derived from testing system 10 withknown amounts of total chlorine to calculate a level of total chlorinein the water under test. This result can be displayed on a displaydevice (e.g., a display device or tablet 112 of dialysis machine 100 ordisplay device 62 of water purification machine 50). Alternatively oradditionally, an indicator (such as an audible alarm and/or a visualalarm) can be used to notify a user when the amount of total chlorine inthe water under test is above (or below) a predetermined threshold(e.g., 0.1 ppm).

Water Purification and Dialysis Machine Configuration Using the TotalChlorine Detection System

As discussed herein, water purification machine 50 can house or operatewith the chlorine sensing system 10 of the present disclosure. To thatend, chlorine sensing in system 10 may be in fluid connection with waterpurification machine 50 at any suitable location along the fluid path ofthe machine.

Referring now generally to FIGS. 4 to 7, in one embodiment, waterpurification machine 50 is in fluid connection with a water source 310.Water source 310 may be any water source suitable for home useincluding, for example, a municipal water source or a well water source.In the illustrated embodiment, water purification machine 50 includes awater pretreatment filter 320, which may include any number of filtersand/or sorbents for removing impurities from the water obtained from thewater source 310. In some embodiments, the water pretreatment filter 320includes a carbon filter. In the embodiment shown in FIG. 4, waterpretreatment filter 320 is in fluid connection with chlorine sensingsystem 10 as described herein. In this embodiment, chlorine sensingsystem 10 is also in fluid connection with a reverse osmosis filter 330.The reverse osmosis filter 330 is in turn in fluid connection with adrain 370 and an electrodeionization (“EDI”) module 340, which mayoptionally further include an electrodialysis component. The EDI module340 is in fluid connection with an ultraviolet lamp or filter 350, whichin turn is in fluid connection with a bacterial filter 360. Bacterialfilter 360 may optionally further include an endotoxin filter. Watertreated by water purification machine 50 may be used with a downstreamdialysis machine 100, such as a hemodialysis system or home hemodialysismachine as has been described herein.

As illustrated in FIGS. 5 to 7, chlorine sensing system 10 mayalternatively be in fluid connection with the ultraviolet lamp or filter350 and the bacterial filter 360 (FIG. 5); with the bacterial filter 360and dialysis machine 100 (FIG. 6); or with the water source 310 and thewater pretreatment filter 320 (FIG. 7). In some embodiments, thechlorine sensing system 10 is in fluid connection with the water pathwayof the water purification machine 50 via a sampling port (not shown).

Aspects of the Present Disclosure

Aspects of the subject matter described herein may be useful alone or incombination with one or more other aspect described herein. Withoutlimiting the foregoing description, in a first aspect of the presentdisclosure, a system for determining a level of total chlorine in adialysis water sample, the system includes (i) a water purificationmachine, (ii) a dialysis machine in fluid communication with the waterpurification machine, and (iii) a total chlorine detector in fluidcommunication with the water purification machine, said total chlorinedetector including (a) an iodide reservoir, (b) a reducing agentreservoir, (c) a first chamber in fluid communication with the iodidereservoir and a water sample produced by the water purification machine,(d) a second chamber in fluid communication with the reducing agentreservoir, wherein the first and second chambers are separated by amembrane that allows charge but not fluid to pass between the chambers,(e) an electrode pair associated with a voltage source, wherein oneelectrode of the electrode pair is in contact with iodide fluid and thewater sample mixed in the first chamber and the other electrode of theelectrode pair is in contact with a reducing agent solution in thesecond chamber, and (f) a control unit connected operably to theelectrode pair, the control unit configured to (1) at one time cause thevoltage source to apply a source voltage to the electrode pair and (2)at a second time stop applying the source voltage to the electrode pairand instead monitor a sensed electrical parameter through or across theelectrode pair.

In accordance with a second aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,at least one of the electrodes includes platinum, gold, stainless steel,copper, combinations or alloys thereof.

In accordance with a third aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,at least one of the first and second chambers includes a tube.

In accordance with a fourth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the first and second chambers both include tubes, and wherein the firstchamber is disposed within a lumen of the second tube.

In accordance with a fifth aspect of the present disclosure, which canbe used with the second aspect in combination with any other aspect oraspects listed herein, the membrane is selected from the groupconsisting of: a semipermeable membrane, and a membrane including aplurality of perforations.

In accordance with a sixth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,at least one electrode of the electrode pair includes or is providedwith a resistor.

In accordance with a seventh aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,one electrode of the electrode pair is placed in electricalcommunication with a ground.

In accordance with an eighth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the system includes an agitator in contact with at least one of thefirst and second chambers.

In accordance with a ninth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,tri-iodide is generated when the control unit causes the voltage sourceto apply a source voltage to the electrode pair.

In accordance with a tenth aspect of the present disclosure, which canbe used in combination with any other aspect or aspects listed herein,the control unit can determine an amount of total chlorine in the watersample when the control unit stops applying source voltage to theelectrode pair and instead monitors a sensed electrical parameterthrough or across the electrode pair.

In accordance with an eleventh aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the control unit is configured to sequentially (1) at one timecause the voltage source to apply a source voltage to the electrode pairand (2) at a second time stop applying the source voltage to theelectrode pair and instead monitor a sensed electrical parameter throughor across the electrode pair multiple times.

In accordance with a twelfth aspect of the present disclosure, which canbe used with the eleventh aspect in combination with any other aspect oraspects listed herein, the control unit is further configured to mergeresults obtained from performing (1) at one time cause the voltagesource to apply a source voltage to the electrode pair and (2) at asecond time stop applying the source voltage to the electrode pair andinstead monitor a sensed electrical parameter through or across theelectrode pair multiple times.

In accordance with a thirteenth aspect of the present disclosure, whichcan be used with any other aspect or aspects listed herein, the systemis embedded into the water purification machine enabling at least onefilter of the water purification machine to be evaluated.

In accordance with a fourteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the total chlorine detector is downstream of a water filterincluding carbon.

In accordance with a fifteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the system includes a user interface configured and arranged toindicate at least one of (a) an alarm to a user if a level of totalchlorine in the water sample exceeds a predetermined value or (b)indicate a safe status to a user if the level of total chlorine in thewater sample falls below a predetermined value.

In accordance with a sixteenth aspect of the present disclosure, whichcan be used with the fifteenth aspect in combination with any otheraspect or aspects listed herein, the predetermined value of totalchlorine is between and including 0.1 ppm to 0.5 ppm.

In accordance with a seventeenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, at least one of the first chamber, the iodide reservoir, or thereducing agent reservoir is provided in a replaceable cartridge orcassette form.

In accordance with an eighteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the system includes a plurality of pumps and valves positionedand arranged to meter preset amounts of sample water and iodide reagentinto the first chamber and reducing agent into the second chamber.

In accordance with a nineteenth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the system includes at least one pump and valve positioned andarranged to pump deionized water into at least one of the first andsecond chambers.

In accordance with a twentieth aspect of the present disclosure, whichcan be used in combination with any other aspect or aspects listedherein, the system includes at least one pump and valve positioned andarranged to pull fluid from at least one of the first and secondchambers to drain.

In accordance with a twenty-first aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, the system is provided as part of the water purification machinefeeding water to the dialysis machine that prepares dialysate using thewater from the water purification machine, and wherein informationconcerning the level total chlorine is displayed on a user interface ofthe dialysis machine.

In accordance with a twenty-second aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, a method of providing a hemodialysis treatment to a subject inneed thereof, the method includes (i) providing a system as describedherein, wherein the water sample is from water for preparing dialysate,and (ii) determining a level of total chlorine in the water sample,(iii) alerting the user to perform a corrective action if the level oftotal chlorine exceeds a predetermined level, and (iv) allowing the userto perform the hemodialysis treatment if the level of total chlorine isbelow the predetermined level.

In accordance with a twenty-third aspect of the present disclosure,which can be used with the twenty-second aspect in combination with anyother aspect or aspects listed herein, an alerting step further includespreventing the user from performing the hemodialysis treatment until asubsequent level of total chlorine in a subsequent water sample is belowthe predetermined level.

In accordance with a twenty-fourth aspect of the present disclosure,which can be used with the twenty-second aspect in combination with anyother aspect or aspects listed herein, a water sample is from water forpreparing dialysate that has been passed through a filter includingcarbon.

In accordance with a twenty-fifth aspect of the present disclosure,which can be used in combination with any other aspect or aspects listedherein, a method of for determining an amount of total chlorine in waterfor dialysis, the method includes (i) providing a water purificationmachine in fluid communication with a dialysis machine, (ii) providing atotal chlorine detection system, in fluid communication with the waterpurification machine, the total chlorine detection system including afirst chamber in fluid communication with an iodide reservoir and awater sample source, a second chamber in fluid communication with areducing agent reservoir, and an electrode pair associated with avoltage source, wherein one electrode of the electrode pair is incontact with an iodide fluid in the first chamber and the otherelectrode of the electrode pair is in contact with a reducing agentsolution in the second chamber, and wherein the first and secondchambers are separated by a membrane that allows charge but not fluid topass between the chambers, (iii) providing the water sample, the watersample including an amount of total chlorine, (iv) measuring abackground voltage V_(B) in the electrode pair, the background voltageV_(B) associated with any tri-iodide present in the system beforeintroduction of the water sample, (v) metering an amount of the watersample into the system, (vi) monitoring a baseline voltage V₀ via theelectrode pair, the baseline voltage V₀ associated with system after theat least partially purified water sample is provided by the waterpurification machine but before tri-iodide is generated by applying avoltage to the electrode pair, (vii) generating a first amount oftri-iodide from the water sample by applying a voltage V₁ to theelectrode pair for a time t₁, (viii) thereafter monitoring a firstvoltage V₂ in the electrode pair, optionally for a time t₂, the firstmonitored voltage V₂ associated with the sum of the amount of totalchlorine and the first amount of generated tri-iodide, (ix) thereaftergenerating a second amount of tri-iodide from the water sample byapplying a voltage V₃ to the electrode pair for a time t₃, (x)thereafter monitoring a second voltage V₄ in the electrode pair,optionally for a time t₄, the second monitored voltage V₄ associatedwith the sum of the amount of total chlorine and the first and secondamounts of generated tri-iodide, (xi) thereafter optionally generating athird amount of tri-iodide from the water sample by applying a voltageV₅ to the electrode pair for a time t₅, the third amount of tri-iodidecorresponding to the third amount of tri-iodide, (xii) optionallymonitoring a third voltage V₆ in the electrode pair, optionally for atime t₆, the third monitored voltage V₆ associated with the sum of theamount of total chlorine and the first, second and third amounts ofgenerated tri-iodide, and (xiii) calculating the amount of totalchlorine in the water sample from the baseline voltage V₀, thebackground voltage V_(B), and at least one of the first, second andoptional third monitored voltages V₂, V₄ and V₆.

In accordance with a twenty-sixth aspect of the present disclosure, anyof the structure and functionality illustrated or described inconnection with FIGS. 1 to 7 can be used in combination with any otheraspect or aspects listed herein.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

What is claimed is:
 1. A dialysis system comprising: a waterpurification machine producing at least partially purified waterincluding an at least partially purified water sample; a dialysismachine for providing a dialysis treatment to a patient, the dialysismachine receiving the at least partially purified water from the waterpurification machine to prepare dialysis fluid for the dialysistreatment; and a total chlorine detector configured to (i) receive theat least partially purified water sample, (ii) at a first time apply asource voltage to the at least partially purified water sample, and(iii) at a second time stop applying the source voltage to the at leastpartially purified water sample and instead monitor a sensed electricalparameter to determine an amount of total chlorine in the at leastpartially purified water sample.
 2. The dialysis system of claim 1,wherein the total chlorine detector includes an electrode pairassociated with the voltage source, wherein the electrode pair is incontact with the at least partially purified water sample.
 3. Thechlorine detector of claim 2, wherein one electrode of the electrodepair is placed in electrical communication with a ground.
 4. Thedialysis system of claim 1, wherein the total chlorine detector isconfigured to sequentially perform (i) and (ii) multiple times.
 5. Thedialysis system of claim 4, wherein the total chlorine detector isconfigured to merge results obtained from performing (i) and (ii)multiple times.
 6. The dialysis system of claim 1, wherein the totalchlorine detector is incorporated within the water purification machineand configured to evaluate at least one filter of the water purificationmachine.
 7. The dialysis system of claim 1, wherein the waterpurification machine includes carbon purification and the total chlorinedetector is located downstream from the carbon purification.
 8. Thedialysis system of claim 1, further comprising a user interfaceconfigured to indicate to a user at least one of: (i) an alarm if theamount of total chlorine in the at least partially purified water sampleexceeds a predetermined value, or (ii) a safe status if the amount oftotal chlorine in the at least partially purified water sample ismaintained below the predetermined value.
 9. The dialysis system ofclaim 8, wherein the predetermined value is a value within a rangeincluding 0.1 ppm total chlorine to 0.5 ppm total chlorine.
 10. Thedialysis system of claim 1, wherein information concerning the amount oftotal chlorine is displayed in a user interface of the dialysis machine.11. A method of providing a hemodialysis treatment to a subject usingthe system of claim 1, the method comprising: determining the amount oftotal chlorine in the at least partially purified water sample; alertingthe user to perform a corrective action if the amount of total chlorineexceeds a predetermined value; and preparing the dialysis fluid for thedialysis treatment if the amount of total chlorine is below thepredetermined value.
 12. A method of determining an amount of totalchlorine in a water sample for a hemodialysis treatment, the methodcomprising: producing, via a water purification machine, an at leastpartially purified water sample; receiving, in a total chlorinedetector, the at least partially purified water sample from the waterpurification machine; applying at a first time, via the total chlorinedetector, a source voltage to the at least partially purified watersample; removing at a second time, via the total chlorine detector, thesource voltage to the at least partially purified water sample;measuring, after the second time, via the total chlorine detector, anelectrical parameter of the at least partially purified water sample;and determining, via the total chlorine detector, the amount of totalchlorine in the at least partially purified water sample based on themeasured electrical parameter.
 13. The method of claim 12, wherein thetotal chlorine detector is included within at least one of the waterpurification machine or a dialysis machine that receives at leastpartially purified water from the water purification machine.
 14. Themethod of claim 12, wherein the electrical parameter includes at leastone of a current or a voltage difference.
 15. The method of claim 12,wherein the source voltage is applied for a time between one minute andten minutes.
 16. The method of claim 12, wherein the steps of applyingthe source voltage, removing the source voltage, and monitoring theelectrical parameter are sequentially performed multiple times.
 17. Themethod of claim 16, further comprising merging, via the total chlorinedetector, results obtained from performing multiple times the steps ofapplying the source voltage, removing the source voltage, and monitoringthe electrical parameter.
 18. The method of claim 12, furthercomprising: determining, via a total chlorine detector, if the amount oftotal chlorine in the at least partially purified water sample exceeds apredetermined value; and provide an alarm, via a user interface, whenthe amount of total chlorine exceeds the predetermined value.
 19. Themethod of claim 18, further comprising: determining, via a totalchlorine detector, if the amount of total chlorine in the at leastpartially purified water sample is maintained below a predeterminedvalue; and provide a safe status indication, via the user interface,when the amount of total chlorine is maintained below the predeterminedvalue.
 20. The method of claim 19, wherein the predetermined value is avalue within a range between and including 0.1 ppm total chlorine to 0.5ppm total chlorine.
 21. A system performing the method of claim 12, thesystem including the water purification machine, the total chlorinedetector, and a dialysis machine that receives at least partiallypurified water from the water purification machine.